use std::fmt::Debug;

use super::diff::DiffStatus;
use super::sexp::unquote;
use super::sexp::Token;
use super::util::get_property;
use super::util::get_property_quoted_string;
use super::util::get_property_unquoted_atom;

#[derive(Debug)]
pub(crate) enum EmacsField<'s> {
    Required(&'s str),
    #[allow(dead_code)]
    Optional(&'s str),
}

/// Do no comparison.
///
/// This is for when you want to acknowledge that a field exists in the emacs token, but you do not have any validation for it when using the compare_properties!() macro. Ideally, this should be kept to a minimum since this represents untested values.
#[allow(dead_code)]
pub(crate) fn compare_noop<'b, 's, 'x, R, RG>(
    _emacs: &'b Token<'s>,
    _rust_node: R,
    _emacs_field: &'x str,
    _rust_value_getter: RG,
) -> Result<Option<(DiffStatus, Option<String>)>, Box<dyn std::error::Error>> {
    Ok(None)
}

/// Do no comparison.
///
/// This is for when you want to acknowledge that a field exists in the emacs token, but you do not have any validation for it when using the compare_properties!() macro. Ideally, this should be kept to a minimum since this represents untested values.
#[allow(dead_code)]
pub(crate) fn compare_identity() -> () {
    ()
}

/// Assert that the emacs value is always nil or absent.
///
/// This is usually used for fields which, in my testing, are always nil. Using this compare function instead of simply doing a compare_noop will enable us to be alerted when we finally come across an org-mode document that has a value other than nil for the property.
pub(crate) fn compare_property_always_nil<'b, 's, 'x, R, RG>(
    emacs: &'b Token<'s>,
    _rust_node: R,
    emacs_field: &'x str,
    _rust_value_getter: RG,
) -> Result<Option<(DiffStatus, Option<String>)>, Box<dyn std::error::Error>> {
    let value = get_property(emacs, emacs_field)?;
    if value.is_some() {
        let this_status = DiffStatus::Bad;
        let message = Some(format!(
            "{} was expected to always be nil: {:?}",
            emacs_field, value
        ));
        Ok(Some((this_status, message)))
    } else {
        Ok(None)
    }
}

pub(crate) fn compare_property_quoted_string<
    'b,
    's,
    'x,
    R,
    RV: AsRef<str> + std::fmt::Debug,
    RG: Fn(R) -> Option<RV>,
>(
    emacs: &'b Token<'s>,
    rust_node: R,
    emacs_field: &'x str,
    rust_value_getter: RG,
) -> Result<Option<(DiffStatus, Option<String>)>, Box<dyn std::error::Error>> {
    let value = get_property_quoted_string(emacs, emacs_field)?;
    let rust_value = rust_value_getter(rust_node);
    if rust_value.as_ref().map(|s| s.as_ref()) != value.as_ref().map(String::as_str) {
        let this_status = DiffStatus::Bad;
        let message = Some(format!(
            "{} mismatch (emacs != rust) {:?} != {:?}",
            emacs_field, value, rust_value
        ));
        Ok(Some((this_status, message)))
    } else {
        Ok(None)
    }
}

pub(crate) fn compare_property_unquoted_atom<'b, 's, 'x, R, RG: Fn(R) -> Option<&'s str>>(
    emacs: &'b Token<'s>,
    rust_node: R,
    emacs_field: &'x str,
    rust_value_getter: RG,
) -> Result<Option<(DiffStatus, Option<String>)>, Box<dyn std::error::Error>> {
    let value = get_property_unquoted_atom(emacs, emacs_field)?;
    let rust_value = rust_value_getter(rust_node);
    if rust_value != value {
        let this_status = DiffStatus::Bad;
        let message = Some(format!(
            "{} mismatch (emacs != rust) {:?} != {:?}",
            emacs_field, value, rust_value
        ));
        Ok(Some((this_status, message)))
    } else {
        Ok(None)
    }
}

pub(crate) fn compare_property_list_of_quoted_string<
    'b,
    's,
    'x,
    R,
    RV: AsRef<str> + std::fmt::Debug,
    RI: Iterator<Item = RV>,
    RG: Fn(R) -> Option<RI>,
>(
    emacs: &'b Token<'s>,
    rust_node: R,
    emacs_field: &'x str,
    rust_value_getter: RG,
) -> Result<Option<(DiffStatus, Option<String>)>, Box<dyn std::error::Error>> {
    let value = get_property(emacs, emacs_field)?
        .map(Token::as_list)
        .map_or(Ok(None), |r| r.map(Some))?;
    let rust_value = rust_value_getter(rust_node);
    // TODO: Seems we are needlessly coverting to a vec here.
    let rust_value: Option<Vec<RV>> = rust_value.map(|it| it.collect());
    match (value, &rust_value) {
        (None, None) => {}
        (None, Some(_)) | (Some(_), None) => {
            let this_status = DiffStatus::Bad;
            let message = Some(format!(
                "{} mismatch (emacs != rust) {:?} != {:?}",
                emacs_field, value, rust_value
            ));
            return Ok(Some((this_status, message)));
        }
        (Some(el), Some(rl)) if el.len() != rl.len() => {
            let this_status = DiffStatus::Bad;
            let message = Some(format!(
                "{} mismatch (emacs != rust) {:?} != {:?}",
                emacs_field, value, rust_value
            ));
            return Ok(Some((this_status, message)));
        }
        (Some(el), Some(rl)) => {
            for (e, r) in el.iter().zip(rl) {
                let e = unquote(e.as_atom()?)?;
                let r = r.as_ref();
                if e != r {
                    let this_status = DiffStatus::Bad;
                    let message = Some(format!(
                        "{} mismatch (emacs != rust) {:?} != {:?}",
                        emacs_field, value, rust_value
                    ));
                    return Ok(Some((this_status, message)));
                }
            }
        }
    }
    Ok(None)
}